1. Field of the Invention
The present invention relates to a loudspeaker wherein the weight ratio between a vibrating part and a surround of the loudspeaker is adjusted to be within a predetermined range so that the loudspeaker reproduces sound of improved quality. Specifically, the present invention relates to a thin loudspeaker having a diaphragm whose height is relatively lower than its diameter so that the loudspeaker reproduces sound with improved quality.
2. Description of the Related Art
Recently, there have been increasing demands for thinner and lighter loudspeakers. In general, a loudspeaker includes a frame, a surround, a magnetic circuit section, a vibrating section, etc.
FIG. 24 is a cross-sectional view showing a structure of a conventional loudspeaker 100. The conventional loudspeaker 100 includes a voice coil 101, a diaphragm 102, a spider 103, a surround 104, a frame 105, and a dust cap 110. The voice coil 101, the diaphragm 102, the spider 103, and the dust cap 110 form a vibrating section of the conventional loudspeaker 100.
The voice coil 101 is attached to the internal periphery of the diaphragm 102 and connected to the frame 105 through the spider 103. The external periphery of the diaphragm 102 is connected to the frame 105 through the surround 104. The dust cap 110 is attached to the internal periphery of the diaphragm 102.
In the conventional loudspeaker 100, the weight ratio between the vibrating section (formed by the voice coil 101, the diaphragm 102, the spider 103, and the dust cap 110) and the surround 104 is 4:1. The diaphragm 102 has a diameter of 120 mm and a height of 12 mm (diameter:height =1:0.1).
FIG. 25 shows a sound pressure frequency characteristic of the conventional loudspeaker 100 having a structure shown in FIG. 24. In the graph of FIG. 25, the horizontal axis represents the frequency, and the vertical axis represents the sound pressure level. As seen in a region X encircled by a broken line, in the conventional loudspeaker 100, a large turbulence of the sound pressure level occurs in a middle frequency band of 200 Hz to 1 kHz. (Hereinafter, such a turbulence is referred to as xe2x80x9cturbulence of the sound pressure level in the middle bandxe2x80x9d.)
In order to improve a space factor of a loudspeaker, it is effective to reduce the height of the loudspeaker so as to obtain a thin loudspeaker. For obtaining a thin loudspeaker, it is necessary to reduce the height of a diaphragm of the loudspeaker. However, when the height of a diaphragm is reduced, the strength of the external periphery of the diaphragm decreases. In the case where an electric signal is applied to a loudspeaker which uses such a diaphragm of reduced height so as to allow the diaphragm to vibrate, a large resonance occurs at the surround of the loudspeaker and the external periphery of the diaphragm. This resonance causes a turbulence of the sound pressure level in the middle band of 200 Hz to 1 kHz.
According to one aspect of the present invention, a loudspeaker includes: a frame; a vibrating section including a diaphragm having an internal periphery and an external periphery, a voice coil attached to the internal periphery of the diaphragm, a spider which connects the voice coil to the frame, and a dust cap attached to the internal periphery of the diaphragm; and a surround which connects the external periphery of the diaphragm to the frame, wherein the ratio between the weight of the vibrating section and the weight of the surround is 0.9:1 to 1.5:1.
In one embodiment of the present invention, the ratio between the diameter of the diaphragm and the height of the diaphragm is (1:0.2) or greater.
In another embodiment of the present invention, the vibrating section further includes a connector for connecting the diaphragm and the spider to the voice coil.
In still another embodiment of the present invention, a cross-section of the surround has a generally half-circle shape; and at least one protrusion is provided on the surround.
In still another embodiment of the present invention, the at least one protrusion is provided on the surround according to a predetermined pattern along a periphery of the surround.
In still another embodiment of the present invention, the at least one protrusion is provided on the surround at random.
In still another embodiment of the present invention, at least one of the at least one protrusion has a circular shape.
In still another embodiment of the present invention, the at least one protrusion is formed of a same material as that of the surround.
In still another embodiment of the present invention, the at least one protrusion is formed of a material different from that of the surround.
In still another embodiment of the present invention, an internal loss or viscosity of a material used in the protrusion is higher than that of a material used in the surround.
In still another embodiment of the present invention, the at least one protrusion is filled with a material which has a specific gravity greater than that of the surround.
In still another embodiment of the present invention, the surround includes a first film having a cross-section of a generally half-circle shape, a second film having a cross-section of a generally half-circle shape, and at least one weight formed of a material whose density is higher than those of the first and second films; and the at least one weight is sandwiched by the first and second films.
In still another embodiment of the present invention, a gap is provided between the first and second films; and the gap is filled with a liquid, a liquid in the form of gel, or a viscoelastic body.
In still another embodiment of the present invention, the surround has a cavity which has a cross-section of a generally circular shape.
In still another embodiment of the present invention, the cavity of the surround is filled with a liquid, a liquid in the form of gel, or a viscoelastic body.
Thus, the invention described herein makes possible the advantages of providing a thin loudspeaker where the height of a diaphragm is relatively small with respect to the diameter of the diaphragm and which can produce sound with a small turbulence of the sound pressure level in the middle band.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.